4 What type of mass wasting took place in La Conchita? The neighborhood of La Conchita has suffered from large landslides in the recent past that have wiped out homes and even killed people. Debris-flow source areas are often associated with steep gullies, and debris-flow deposits are usually indicated by the presence of debris fans at the mouths of gullies. Heavy rains of January 1995 led to a March 4, 1995, landslide in the La Conchita Community of Ventura County (County), California. Landslides are a type of "mass wasting" which denotes any down slope movement of soil and rock under the direct influence of gravity. Although landslides are primarily associated with mountainous regions, they can also occur in areas of generally low relief. The volume of the landslide was estimated to be approximately 200,000 cubic meters with a surface 350 meters (1,150 feet) long and 80100 meters (260330 ft) wide. La Conchita is located on the southern California coastline midway between Ventura and Santa Barbara (fig. However, dry flows of granular material are also possible. The storm of March 23 also may have played a role in triggering initial movement of the hillside, which already was approaching instability due to longerterm seasonal rises in groundwater levels. Several smaller, more recent slumps and earth flows also are visible, as is the 1995 slumpearth flow (terminology after Varnes, 1978). The most important fluidizing agent is water, but trapped air is sometimes involved. Figure 3: Some major types of mass movements. Ultimately, the County prevailed against the plaintiffs on all claims. Near a Slope? Even modest rain storms during normal, non-El Nio years can trigger post-wildfire debris flows. Early Warning System for Southern California. Figure 1: Air photo of La Conchita, CA taken in 2002. It is likely that the new rainfall did not enter the deposits left behind after the 1995 landslide, but slid off it taking surface debris and few new materials with it. An official website of the United States government. Wave energy is also typically higher during the winter, and particularly during El Nio events, thereby exacerbating the potential for coastal erosion. You also have the option to opt-out of these cookies. Rockfall. Wildfire can significantly alter the hydrologic response of a watershed to the extent that even modest rainstorms can produce dangerous flash floods and debris flows. Do you know what type of landslide occurred in La Conchita? 3H). The content on this page is copyrighted under a Creative Commons Attribution 4.0 International license. In this report, empirical models are used to predict the probability and magnitude of debris-flow occurrence in response to a 10-year rainstorm for the 2013 Springs fire in Ventura County, California. Another factor that affects the shear strength of a slope-forming material is the spatial disposition of its constituent particles, referred to as the sediment fabric. The USGS has a long history of research to identify landslide hazards in southern California (seeSouthern California LandslidesAn Overview- Fact Sheet 2005-3107). Inspection of the site within a few hours of the landslide indicated that much of the deposit consisted of fairly dry material (James O'Tousa, RJR Engineering, personal commun., 2005). 7). Shear strength is dependent mainly on two factors: frictional strength, which is the resistance to movement between the slope materials interacting constituent particles, and cohesive strength, which is the bonding between the particles. Although many types of mass movements are included in the general term landslide, the more restrictive use of the term refers only to mass movements, where there is a distinct zone of weakness that separates the slide material from more stable underlying material. If significant additional rainfall occurs, either this year or in future years, several landslide scenarios are possible: (a)deep movement of the 1995 deposit, as described above, (b) mobilization of the 1995 (and possibly the 2005) deposit into a rapid debris flow such as occurred on January 10, 2005, (c) triggering of subsidiary landslides from parts of the 1995 and 2005 deposits or scarps, (d) triggering of slumps and (or) earth flows on adjacent hillsides, and (e) triggering of rapid debris flows from various nearby slopes, particularly in ravines. https://www.britannica.com/science/landslide, Geology.com - Landslide Hazard Information. Figure 1: Air photo of La Conchita, CA taken in 2002. Figure 8 shows an aerial photograph of La Conchita taken in September 2004. Note the numerous landslides that have taken place in the area, including the large slide in 1995. What experience do you need to become a teacher? Shear stresses can be built up within a slope by a number of processes. After covering the road with 7-8 feet of debris, the slide stabilized. How can the hazards of landslides to humans be mitigated? Some, but not all, of the major winter storms that have caused landslide fatalities and property damage in southern California have occurred duringEl Nio(1997-98 info) conditions. The landslide recurred on part of a previous landslide in 1995.La Conchita, California. The failure starts suddenly in a small area and spreads rapidly. The 2005 La Conchita landslide occurred at about 12:30 p.m. on January 10. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. What was the main cause of La Conchita landslide in 2005? The bluff above La Conchita consists of poorly indurated marine sediment of the Monterey and Pico Formations. landslide, also called landslip, the movement downslope of a mass of rock, debris, earth, or soil (soil being a mixture of earth and debris). But opting out of some of these cookies may affect your browsing experience. YUARA SLUMP EARTHFLOW DEBRIS SLIDE ROCKFALL SCARP ORIGINAL LAND SURFACE -SLIP PLANE.
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